三维多段线的Z坐标怎么取

Private Sub GetLWPOLYLINECoordinates()
    Dim ss_dim As AcadSelectionSet, ent As AcadEntity
    Dim dxf_code() As Integer, dxf_value() As Variant
    Dim i As Long, j As Long
    Dim dbCor As Variant, x As Double, y As Double, z As Double
    On Error GoTo ErrExit
    Set ss_dim = ThisDrawing.SelectionSets.Add("sPolyLines")
    ReDim dxf_code(3), dxf_value(3)
    dxf_code(0) = -4: dxf_value(0) = "<OR"
    dxf_code(1) = 0: dxf_value(1) = "LWPOLYLINE" '这里表示2D多义线
    dxf_code(2) = 0: dxf_value(2) = "POLYLINE" '这里表示3D多义线
    dxf_code(3) = -4: dxf_value(3) = "OR>"

    ss_dim.Select acSelectionSetAll, , , dxf_code, dxf_value

    Open "d:\aaaaa.txt" For Append As #1
    '"AcDb3dPolyline","AcDbPolyline"
    For Each ent In ss_dim
        Select Case ent.ObjectName
        Case "AcDb3dPolyline"'这里处理3D多义线坐标
            Dim ent3D As Acad3DPolyline
            Set ent3D = ent
            For j = 0 To UBound(ent3D.Coordinates) \ 3
                x = ent3D.Coordinates(j * 3)
                y = ent3D.Coordinates(j * 3 + 1)
                z = ent3D.Coordinates(j * 3 + 2)
                Print #1, "X" & x & ",Y" & y & ",Z" & z
            Next
        Case "AcDbPolyline"'这里处理2D多义线坐标
            Dim ent2D As AcadLWPolyline
            Set ent2D = ent
            For j = 0 To UBound(ent2D.Coordinates) \ 2
                x = ent2D.Coordinates(j * 2)
                y = ent2D.Coordinates(j * 2 + 1)
                Print #1, "X" & x & ",Y" & y & ",Z" & ent2D.Elevation
            Next
        End Select
    Next
ErrExit:
    ss_dim.Clear
    ss_dim.Delete
    Close #1
End Sub